Carbon-halogen Bond Cleavage Energies of Alkyl Halides and Haloalkyl Radical Anions in Solution

Radical anions are intermediates in a variety of processes:dissolving metal reductions, cathodic reductions⁽¹⁾,homogeneous redox reactions, S_RN² reactions⁽²⁾ and nucleophilic substitions⁽³⁾. Several techniques ranging from pulse rediolysis, near-infrared spectroscopy, derivative linear-sweep voltammetry, and electron spin resonance spectroscopy have been employed to study the characteristic properties of the radical anions. The most characteristic property for the radical anions derived from organic halides, in particular, has been known to be the severe weakening of the carbon-halogen bond and consequently the ease of its dissociative cleavage to form halide ion and radical (eq.l) or to form halogen atom and anion (eq.2) as seen in the key step of the S_RN¹ mechanism.